Testing Main Paths with System Tests

@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class SendMoneySystemTest {
  @Autowired
  private TestRestTemplate restTemplate;
  @Test
  @Sql("SendMoneySystemTest.sql")
  void sendMoney() {
  
    Money initialSourceBalance = sourceAccount().calculateBalance();
    Money initialTargetBalance = targetAccount().calculateBalance();
  
    ResponseEntity response = whenSendMoney(
        sourceAccountId(),
        targetAccountId(),
        transferredAmount());
  
    then(response.getStatusCode())
        .isEqualTo(HttpStatus.OK);
  
    then(sourceAccount().calculateBalance())
        .isEqualTo(initialSourceBalance.minus(transferredAmount()));
  
    then(targetAccount().calculateBalance())
        .isEqualTo(initialTargetBalance.plus(transferredAmount()));
  
  }
  private ResponseEntity whenSendMoney(
      AccountId sourceAccountId,
      AccountId targetAccountId,
      Money amount) {
    
    HttpHeaders headers = new HttpHeaders();
    headers.add("Content-Type", "application/json");
    HttpEntity<Void> request = new HttpEntity<>(null, headers);
  
    return restTemplate.exchange(
        "/accounts/sendMoney/{sourceAccountId}/{targetAccountId}/{amount}",
        HttpMethod.POST,
        request,
        Object.class,
        sourceAccountId.getValue(),
        targetAccountId.getValue(),
        amount.getAmount());
  }
    // some helper methods omitted 
}